The present invention relates to the manufacture of containers. In another aspect, the present invention relates to an improved method of manufacturing flexible containers for use in the transportation, storage and handling of flowable materials.
Flowable materials, and particularly dry particulate materials present unique problems in their storage, transportation, dispensing and handling. These materials, for example, include chemicals, fertilizers, minerals, food stuffs, agricultural products, and the like.
One system of handling these materials utilizes an improved flexible receptacle which can be easily handled, has a large capacity, and provides top filling and bottom discharge. These receptacles utilize an outer protective covering of flexible sheet material which can be doubled for additional strength. A double-walled interior bag is provided which is formed from sheet material. A high strength filament is wound in a helix around the exterior surface of a double-walled interior bag and is secured thereto by a non-curing mastic adhesive. A sling of flexible webbing material forms a frame for the receptacle and has an inner ring which supports the bottom of the receptacle and an outer, larger ring which is positioned above the inner ring to prevent formation of pockets in the container and to facilitate complete unassisted discharge of the materials from the container. Loops of the webbing interattach the upper and lower rings. The loops are attached to the inside of the outer protective covering and extend above the top thereof for use in supporting the receptacle by appropriate transporting apparatus. Removable wire ties are provided for closing the gathered ends of the top and bottom of the inner bag to allow top loading and bottom discharge of materials therein.
Although receptacles of this type have been quite adequate for handling bulk particulate materials, they have conventionally required substantial amounts of labor in their manufacture. Therefore, according to one feature of the present invention, an improved method of manufacturing a flexible material handling receptacle is disclosed.
According to a particular feature of the present invention, a method of manufacturing a receptacle having a double-walled interior bag with an outer protective covering formed from flexible sheet material is disclosed. A filament is wound in a helix around the exterior surface of the interior bag and a sling of webbing forms a frame for the receptacle. Removable wire ties are applied to the gathered ends of the interior bag to allow top loading and bottom discharge of the material therefrom.
More particularly, the present invention provides a method for fabricating receptacles for transporting dry flowable material wherein a first cylindrical wall of sheet material is located in a work area, a second cylindrical wall of sheet material is concentrically positioned around the first wall, and a filament is attached to the exterior of said second wall. A sling is then attached to the exterior of said second wall and the filament by an adhesive material. A protective covering is wrapped around the exterior of the sling, the filament and the second cylindrical wall, and the ends of the first and second cylindrical walls are gathered together and releasably closed with wire ties.
Two embodiments of the invention are disclosed. In one embodiment, the first and second walls are formed by wrapping a sheet around a mandrel to form two layers thereon, and slitting the interconnection between the layers adjacent to their opposite ends. In another embodiment, the first and second walls are formed by positioning tubular members one over the other on the mandrel.